In wireless communications systems, video and images are sent by encoding image data bits onto a bit stream. When transmit as a wireless signal the bit stream exhibits frequency characteristics that include a frequency spectrum shape that relates directly to signal quality and how the signal should be processed for transmission. Normally a wireless communications system is designed so that the system can handle the spectrum shape of transmitted video and images without causing unacceptable interference or loss of data.
In some cases, it may be desirable to send information as data bits embedded in a transmitted image by replacing certain it data bits with information data bits. For example, information (such as hidden watermarks, overlying captions or text that is to appear in the image) may be sent by superimposing data bits of the information onto the image data bits. In conventional techniques the information bits are embedded or superimposed in place of image bits in certain image pixels, for example in a section at the top of an image. This is done without consideration beforehand of how the removal of image bits, and how the placing and embedding of information bits, will affect the shape of the transmitted image's frequency spectrum and the quality of an image. These effects on the frequency spectrum and image quality may be detrimental and cause unacceptable interference and loss of image data.
In existing systems, the effects on the shape of a transmitted image's frequency spectrum and the transmitted image's quality caused by removing image pixels and adding information bits are handled by using complicated techniques for coding/decoding and processing the transmitted and received image signals at the receiver. In some cases, critical image information may be lost and not be recoverable, and received image quality may not be acceptable.